TREATMENT AND
DISPOSAL OF BYPRODUCTS OF SLAUGHTER
4TH YEAR LECTURE
4 th year Lecture
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Main product of slaughter is carcass meat
 Definition – everything from abattoir or butcher
shop not sold directly as food or not carcass
meat
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Why treat?
 Rapid hygienic disposal,
 Avoid decomposition
 Avoid obnoxious odors
 Avoid contamination of fresh meat
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Why process?
◦ Brings economic returns
 By- products are divided into edible and
inedible
 Edible by-products e.g. liver, kidneys, thymus ,
pancreas, edible blood, fat, tripe
 Inedible include bone, hooves, hides and skins
 When edible by-products are affected by
conditions that make them unfit for human
consumption- inedible
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FATS
 Sources – trimmings from kidney,
intestines, channel and other organs
 Edible fat processed into oleo oil and oleo
stearin
 Inedible fats processed into soap
manufacturing, glycerine – medicinal
preparations, gun powder, cordite and
dynamite.
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Processing of edible fat
◦ low FFA any processing ensures that FFA
remains low by initial cold storage of raw
material, low processing temperatures and
minimized cooking times
◦ Wet rendering – pre-cut raw materials injected
with steam to 140oC under pressure for 3-4 hrs
◦ Pressure released and fat drains out purified by
gravity or centrifugation- removes water
◦ Greases or proteinaceous solids removed and fat
extracted by solvents
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Dry rendering
◦ Similar to wet rendering but initially uses
steam and water for 1.5 -2 hrs to drive water
out of fat
o Continuous low temperature rendering
uses heating, separation and cooling in a
continuous flow. Material is minced, melting by
steam at 90oC,separation of liquid fat from solids
by centrifugation, heating, centrifugation and
cooling.
During rendering care taken to prevent
breakdown of fat into FFA and glycerides by
lipases active at 40-60oC
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Stomachs and Intestines
 Used in pet foods manufacture
 Human consumption (tripe) if passed fit.

◦ emptied and washed, fat trimmed off, scalded
in water containing soda, scrapped, cooked at
49-60oC.
Rumen contents used for compost, biogas
generation
 Suckling calves, rennet is extracted from
the abomasum
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 When
 Blood
collected hygienically used for human
consumption. Uncontaminated with ingesta,
urine, or foreign material. Originate from healthy
animals
 Blood recovered from animals ranges from 3-4%
of live weight in cattle and pigs; 4-4.5% in
sheep, 3.5-4% in lambs 5-6% in calves.
Anticoagulants are used
 Used to make black pudding (muturas), or for
separation of plasma and red cells.
 Red cells for black pudding or blood meals
 Plasma blood transfusion services.
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Inedible blood collected without due care.
 Dried into blood meal by drying to final water
content of 8-10%; coagulation in batches
draining, pressing and final drying; preheating,
coagulation and separation followed by drying
 Bones
 Amount depends on whether meat is deboned.
 Bones mixed with other condemned material and
into meat and bone meals
 Products of bone processing are fat, bone meal,
gelatine and meat and bone meal.
 Due to its high calcium and phosphorous content
bone meal used in poultry feeds and fertilizers.
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Calcined bone from roasting in air is used in high
class pottery, china, refining of silver and in copper
smelting
Bone charcoal is used in sugar refining, case
hardening in steel manufacture, removal of fluorine in
water (bone powders)
 Hoofs and horns
Hoofs are removed by stepping in hot water then
drying
White hoofs used in the manufacture of combs,
buttons
Stripped and black hoofs are used in hoof meal
fertilizer for grape vines
Horns used for manufacture of hairpins, buttons,
knife handles,. Pig hairs used in making foam-type
fire extinguishers fluids
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Hair and bristles
 Cattle hairs go with the hide, separated by the
tanners used by plasterers as a binding agent
 Used as an insulating material in carpet
manufacture after purification with HCl to
remove lime.
 Long black and tail thistles of pigs – brush
making, shaving brushes, stuffing mattresses
(pigs) after purification
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Hides and Skins
Represents about 12% of value of the animal,
carcass 80% and by-products 7%
 Hide is tanned and made into leather (shoes,
belts) and sole leather.
 Sheep skin into leather for gloves
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DISPOSAL of condemned materials
 sterilization –rendering
 Incineration
 Deep burial pits
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References
◦ Meat Hygiene –Gracey
• Purpose – Understand
• Utilization of different by-products of slaughter
• Disposal methods of condemned material
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